Aluminum pipe having excellent surface quality, method and apparatus for manufacturing the aluminum pipe, and photosensitive drum base body

ABSTRACT

In a manufacturing method in which an aluminum bullet is extruded to obtain an extruded raw pipe  4  and then the extruded raw pipe  4  is subjected to a drawn process, the aluminum extruded raw pipe  4  is cut at a position within 10 m from a discharge position M of an extruding die to obtain an aluminum extruded raw pipe  4  with a length of 10 m or shorter, and the extruded raw pipe  4  is subjected to a drawing process. With this, an aluminum pipe excellent in surface quality having no surface defect such as white peeling can be manufactured at high manufacturing efficiency.

This application claims priority to Japanese Patent Application No. 2003-303334 filed on Aug. 27, 2003, and U.S. Provisional Application filed on Sep. 3, 2003 (Title of the Invention; Aluminum Tube with Excellent Surface Quality, Method and Apparatus for Producing the Same and Photosensitive Drum Substrate, Applicant: Showa Denko K. K., Inventors: Koji IWANAGA, Takeshi GOCHO, Kunihiro SAGAWA, Youichi MOMO, The Notice of Application Number of this provisional application has not yet arrived from the United States Patent and Trademark Office), the entire disclosures of which are incorporated herein by reference in their entireties.

Cross Reference to Related Applications

This application is an application filed under 35 U.S.C. §111(a) claiming the benefit pursuant to 35 U.S.C. §119(e)(1) of the filing date of U.S. Provisional Application filed on Sep. 3, 2003 (Title of the Invention: Aluminum Tube with Excellent Surface Quality, Method and Apparatus for Producing the Same and Photosensitive Drum Substrate, Applicant: Showa Denko K.K., Inventors: Koji IWANAGA, Takeshi GOCHO, Kunihiro SAGAWA, Youichi MOMO, The Notice of Application Number of this provisional application has not yet arrived from the United States Patent and Trademark Office), pursuant to 35 U.S.C. §111(b).

TECHNICAL FIELD

The present invention relates to an aluminum pipe excellent in surface quality preferably used as a photosensitive drum for use in electrophotographic apparatuses such as copying machines, printers or facsimile machines, the manufacturing method and a photosensitive drum substrate excellent in surface quality.

In this specification, the wording aluminum is used to include the meaning of both aluminum and aluminum alloy.

BACKGROUND ART

In an aluminum pipe to be used as a photosensitive drum for use in electrophotographic apparatuses such as copying machines, printers or facsimile machines, by its very nature, it is required to have a surface status relatively closed to a mirror surface. Conventionally, an aluminum pipe was mirror finished by cutting work. However, there were such problems that the adjustment and administration of the cutting tool were not easy and it was not unsuitable for the mass production since the work required skill.

Under the circumstances, in recent years, an aluminum drawn pipe obtained by drawing an aluminum extruded raw pipe, which is called an “ED pipe,” has been popularly used as a photosensitive drum substrate. This ED pipe is manufactured by initially extruding an aluminum billet into an aluminum extruded raw pipe, then cutting the extruded raw pipe into a predetermined length, thereafter subjecting the cut extruded raw pipe to a drawing process to improve the surface quality to thereby obtain an aluminum pipe having a predetermined size (external diameter, internal diameter and thickness), and further washing the aluminum pipe (See JP, S63-188422,A).

In the aluminum drawn pipe manufactured as mentioned above, however, there often occurred very minute and long thready surface defects (hereinafter simply referred to as “white peeling”) extending generally in the drawing direction as shown in the optical microscope photograph of FIG. 14 (In FIG. 14, a white peeling extends from the center of the photographic image toward the obliquely right upward). As a recent photosensitive drum for use in photoelectrographic devices such as copying machines, printers or facsimile machines, a photosensitive drum capable of realizing excellent image quality is demanded. However, with an aluminum pipe having surface defects such as the aforementioned white peeling, it was not able to sufficiently fulfill such a demand. In the aluminum drawn pipes obtained by the above-mentioned conventional manufacturing method, a rate that a good quality product having no surface defect such as a white peeling can be obtained, i.e., a yield rate, was about 70%. Thus, the manufacturing efficiency was very bad. Therefore, there was a pressing need to develop a manufacturing method which does not cause surface defects such as such white peelings.

The present invention was made in view of the aforementioned technical background, and aims to provide a method and an apparatus for manufacturing an aluminum pipe excellent in surface quality without causing surface defects such as white peelings, an aluminum pipe excellent in surface quality, and a photosensitive drum substrate.

Other objects of the present invention will be apparent from the following preferred embodiments.

DISCLOSURE OF INVENTION

In order to attain the above-mentioned purpose, the inventors investigated the cause of generation of the white peelings (surface defects). The inventors initially thought that the following factors caused or influenced the white peelings.

(i) Influence of deviation of a material billet composition (effect of impurity concentration, etc.)

(ii) Degradation of an extruding die and a drawing die

(iii) Influences of a cooling method of a raw pipe after extrusion (air cooling, mist cooling, etc.)

(iv) Degradation of rollers for transporting an extruded raw pipe, Adhesion of foreign substances

(v) Contamination of supporting portions of an extruded raw pipe. Adhesion of foreign substances

(vi) Influence of deviation (instability) of a drawing speed

(vii) Degradation of lubricating oil used at the time of drawing processing, Mixing of foreign substances.

As a result of the careful research and investigation on whether the aforementioned various factors considered to have a high possibility of the cause of the white peeling were the cause of the white peeling, it became clear that none of the above factors (i) to (vii) did not to affect the generation of the white peeling.

Then, the inventors conducted further detail analysis and investigation on the cause of generation of the white peeling. Consequently, the observation of the extruded raw pipe (length: about 50 m) from the extrusion die side to the extrusion direction tip end side using an optical microscope revealed that the incidence rate of white peelings increased toward the extrusion direction tip end side. In other words, it revealed that the occurrence of white peeling was low at the extruding die side. It also revealed that there is a possibility that adhesion of fibers of a felt layer formed on the surface of a roller for transferring the raw pipe immediately after the extrusion is the cause of occurrence of white peeling. Then, in order to confirm it, an extruded raw pipe was drawn in a state in which fibers of a felt layer were intentionally made to adhere to the extruded raw pipe. As a result, it revealed that the same white peeling defects as shown in FIG. 14 occurred and adhesion of the fibers was the cause of the while peeling. It is presumed that a longer contact time of the raw pipe of high temperature immediately after the extrusion with respect to the felt layer of the roller caused burn and adherence of the fiber to the surface of the raw pipe and that the white peeling extending along the drawing direction as shown in FIG. 14 occurred on the surface of the pipe when drawing was performed in this state. From the aforementioned series of various cause investigation and analysis results, it was concluded that, in order to prevent occurrence of white peeling, an aluminum extruded raw pipe should be cut at a position within 10 m from the discharge position of the extruding die to obtain an aluminum extruded raw pipe with a length of 10 m or shorter.

In order to attain the aforementioned objects, the present invention provides the following means.

[1] A method of manufacturing an aluminum pipe excellent in surface quality by extruding an aluminum billet to obtain an aluminum extruded raw pipe and then drawing the aluminum extruded raw pipe,

wherein the extruded aluminum extruded raw pipe is cut at a position within 10 m from a discharge position of an extruding die to obtain an aluminum extruded raw pipe with a length of 10 m or shorter, and the cut aluminum extruded raw pipe is subjected to a drawing process.

[2] A method of manufacturing an aluminum pipe excellent in surface quality, comprising:

an extruding step for extruding an aluminum billet to obtain an aluminum extruded raw pipe;

a cutting step for cutting the extruded aluminum extruded raw pipe at a position within 10 m from a discharge position of an extruding die to obtain an aluminum extruded raw pipe with a length of 10 m or shorter; and

a drawing step for drawing the cut aluminum extruded raw pipe to obtain an aluminum pipe.

[3] The method of manufacturing an aluminum pipe excellent in surface quality as recited in the aforementioned Item 1 or 2, wherein the extruded aluminum extruded raw pipe is cut at the position within 10 m from the discharge position of the extruding die to thereby obtain an aluminum extruded raw pipe with a length of 1 to 6 m.

[4] The method of manufacturing an aluminum pipe excellent in surface quality as recited in the aforementioned Item 1 or 2, wherein the extruded aluminum extruded raw pipe is cut at the position within 7 m from the discharge position of the extruding die to thereby obtain an aluminum extruded raw pipe with a length of 2 to 5 m.

[5] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 4, wherein the extruded aluminum extruded raw pipe is conveyed towards an extruding direction while supporting the raw pipe with a supporting roller having a synthetic fiber felt circumferentially attached on an external peripheral surface of a roller core portion.

[6] The method of manufacturing an aluminum pipe excellent in surface quality as recited in the aforementioned Item 5, wherein a main fiber constituting the felt is an aramid fiber.

[7] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 6, wherein, as the aluminum billet, a billet consisting of Mn: 1.1 to 1.6 mass %, Si: 0.7 mass % or less, Fe: 0.8 mass % or less, Cu: 0.04 to 0.21 mass %, Zn; 0.11 mass % or less, and the balance being aluminum and inevitable impurities is used.

[8] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one the aforementioned Items 1 to 7, wherein the extruding is performed using an extruding die in which an extrusion directional length L of a die bearing portion defining an external surface of the aluminum extruded raw pipe is 5 mm or shorter and a relationship between a peripheral directional center line average roughness Ra(Y) of the bearing portion and an extrusion directional center line average roughness Ra(X) of the bearing portion is set to Ra(Y)<Ra(X).

[9] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 7, wherein the extruding is performed using an extruding die in which a bearing portion is formed of superhard material and surface roughness of the bearing portion is adjusted to 5 to 30 μm in Ry (maximum height).

[10] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 9, wherein peripheral directional surface roughness of the aluminum extruded raw pipe obtained by the cutting is 0.5 to 10 μm in Ry (maximum height).

[11] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 10, wherein, in drawing the aluminum extruded raw pipe after the cutting by pulling the extruded raw pipe between a drawing die and a drawing plug,

the drawing is performed while supplying lubricating oil of 200 cst or less in viscosity between the drawing die and the extruded raw pipe so that an external diameter reduction rate from the extruded raw pipe to an aluminum pipe is 30% or less and a cross-sectional area reduction rate is 5% or more.

[12] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 11, wherein, in drawing the aluminum extruded raw pipe after the cutting by pulling the extruded raw pipe between a drawing die and a drawing plug,

as a rod for supporting the drawing plug, a rod provided with one or a plurality of cores coming into contact with an internal peripheral surface of the extruded raw pipe along an entire length of the extruded raw pipe is used.

[13] The method of manufacturing an aluminum pipe excellent in surface quality as recited in the aforementioned Item 12, wherein a groove parallel to an axis is formed on an external peripheral surface of the core.

[14] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 13, wherein, in drawing the aluminum extruded raw pipe after the cutting by pulling the extruded raw pipe between a drawing die and a drawing plug,

as the drawing die, a die in which an approach angle is set so as to fall within a range of 10 to 40° and a bearing length is set so as to fall within a range of 8 to 25 mm is used, and

as the drawing plug, a plug in which an approach angle is set so as to fall within a range of 6 to 10° and a bearing length is set so as to fall within a range of 1.5 to 3 mm is used.

[15] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 14, wherein the drawing is performed by drawing the aluminum extruded raw pipe having a crystal grain whose average length in a drawing direction is 60 μm or more on a surface of the aluminum extruded raw pipe obtained by the cutting so that the average length of the crystal grain in the drawing direction becomes 1.3 times or more, thereby obtaining an aluminum pipe having a crystal grain whose average length in the drawing direction exceeds 300 μm.

[16] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 15, wherein, after cutting off a chucked portion of the aluminum pipe obtained by the drawing by a press cutting method, straightening of the aluminum pipe is performed using a roll straightening machine.

[17] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 16, wherein the aluminum pipe obtained by the drawing is washed using a solvent with a KB (kauri-butanol) value of 20 or more within three days after the drawing.

[18] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of the aforementioned Items 1 to 17, wherein the aluminum pipe obtained by the drawing is subjected to ultrasonic cleaning by setting a relationship between a frequency f (kHz) of a ultrasonic wave of an ultrasonic wave oscillator and an ultrasonic cleaning time T (minute) to f×T≦120 (kHz·min).

[19] The method of manufacturing an aluminum pipe excellent in surface quality as recited in the aforementioned Item 18, wherein the ultrasonic cleaning is performed by setting a relationship between an output P (W) of the ultrasonic wave oscillator and an ultrasonic oscillation area S (cm²) to 0.1≦P/S≦1.0 (W/cm²).

[20] The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one the aforementioned Items 1 to 19 wherein the aluminum pipe is an aluminum pipe for photosensitive drums.

[21] An aluminum pipe manufactured by the manufacturing method as recited in one of the aforementioned Items 1 to 19.

[22] A photosensitive drum substrate made of an aluminum pipe manufactured by the manufacturing method as recited in one of the aforementioned Items 1 to 19.

[23] An apparatus for manufacturing an aluminum pipe, comprising:

an extruding machine; and

a cutting machine disposed at an extruding direction front position of the extruding machine and configured to execute cutting of the aluminum extruded raw pipe which is being extruded from the extruding machine while moving in synchronization with a traveling speed of the aluminum extruded raw pipe,

wherein the cutting of the aluminum extruded raw pipe with the cutting machine is executed at a position within 10 m from a discharge position of the extruding die of the extruding machine.

[24] The apparatus for manufacturing an aluminum pipe as recited in the aforementioned Item 23, wherein a supporting roller with a synthetic fiber felt circumferentially attached on an external peripheral surface of a roller core portion is disposed between the extruding machine and the cutting machine.

[25] The apparatus for manufacturing an aluminum pipe as recited in the aforementioned Item 24, wherein a main fiber constituting the felt is an aramid fiber.

[26] The apparatus for manufacturing an aluminum pipe as recited in any one of the aforementioned Items 23 to 25, further comprising a control apparatus for controlling execution of an cutting operation of the cutting machine based on information of the traveling speed of the aluminum extruded raw pipe obtained from a speed sensor.

[27] The apparatus for manufacturing an aluminum pipe as recited in any one of the aforementioned Items 23 to 26, wherein the cutting of the aluminum extruded raw pipe with the cutting machine is executed at a position within 7 m from a discharge position of the extruding die of the extruding machine.

[28] An aluminum drawn pipe having substantially no fine thready surface defect extending approximately in a drawing direction on a surface of the aluminum drawn pipe.

[29] A photosensitive drum substrate made of an aluminum drawn pipe having substantially no fine thready surface defect extending approximately in a drawing direction on a surface of the aluminum drawn pipe.

[30] A photosensitive drum with a photosensitive layer formed on an external peripheral surface of the photosensitive drum substrate as recited in claim 22 or 29.

[31] An electrophotographic device constituted by the photosensitive drum as recited in the aforementioned Item 30.

In the invention as recited in the aforementioned Item [1], since an extruded aluminum extruded raw pipe is cut at a position within 10 m from the discharge position of the extruding die to obtain an aluminum extruded raw pipe with a length of 10 m or shorter and then the extruded raw pipe is subjected to a drawing process, an aluminum pipe with no surface defect such as white peeling can be manufactured, which in turn can manufacture an aluminum pipe excellent in surface quality at high manufacturing efficiency. The reason that occurrence of surface defects such as white peelings can be prevented can be assumed that the contact time of, the high temperature extruded raw pipe immediately after extrusion to the surface of the supporting roller is shortened to thereby effectively prevent the fiber of the felt layer from burning and adhering to the raw pipe surface.

In the invention as recited in the aforementioned Item [2], since the extruded aluminum extruded raw pipe is cut at a position within 10 m from the discharge position of the extruding die to obtain an aluminum extruded raw pipe with a length of 10 m or shorter and then the extruded raw pipe is subjected to a drawing process, an aluminum pipe with no surface defect such as white peeling can be manufactured, which in turn can manufacture an aluminum pip excellent in surface quality at high manufacturing efficiency. The reason that occurrence of surface defects such as white peelings can be prevented is assumed that the contact time of the high temperature extruded raw pipe immediately after extrusion to the surface of the supporting roller is shortened to thereby effectively prevent the fiber of the felt layer from burning and adhering to the raw pipe surface.

In the invention as recited in the aforementioned Item [3], occurrence of surface defects such as white peelings can fully be prevented.

In the invention as recited in the aforementioned Item [4], occurrence of surface defects such as white peelings can be assuredly prevented.

In the invention as recited in the aforementioned Item [5], since the extruded aluminum extruded raw pipe is conveyed in the extruding direction while being supported by a supporting roller on which a synthetic fiber felt is attached, the extruded raw pipe can be conveyed while maintaining the good surface status without causing any damage on the surface of the extruded raw pipe.

In the invention as recited in the aforementioned Item [6], since a main fiber constituting the felt is an aramid fiber, the burning and adhering of the fiber of the felt layer to the extruded raw pipe surface (high temperature state) can be more assuredly prevented.

In the invention as recited in the aforementioned Item [7], since composition of the billet is specified so as to fall within the specific range, an aluminum pipe suitably used for photosensitive drums can be manufactured.

In the invention as recited in the aforementioned Item [8], since adhesion/transfer of aluminum particles to the extruded aluminum extruded raw pipe surface can be prevented, surface smoothness can be improved and an aluminum pipe having more excellent surface quality can be manufactured.

In the invention as recited in the aforementioned Item [9], a thin film of the extruding material can be easily formed on the surface of the bearing portion of the extruding die, improving the affinity of the bearing portion and the extruding material, which eases the burning at the time of the extrusion. Thus, an aluminum pipe excellent in surface smoothness can be manufactured.

In the invention as recited in the aforementioned Item [10], since Ry in the peripheral direction of the extruded raw pipe is specified so as to fall within the specific range, occurrence of wrinkle-like defects of an aluminum pipe obtained and pit-like defects due to oil pits can be fully prevented. Therefore, coating stagnation at the time of applying a thin film coating on the surface of the aluminum pipe can be controlled, which in turn enables uniform image formation of a photosensitive drum.

In the invention as recited in the aforementioned Item [11], with the same number of steps as a conventional drawing process, occurrence of concave defects due to oil pits can be controlled, and a die blemish existing on the surface of the extruded raw pipe can be restored. Thus, a drawn pipe high in surface smoothness can be manufactured.

In the invention as recited in the aforementioned Item [12], since one or a plurality of cores coming into contact with an internal peripheral surface of the extruded raw pipe are provided to the rod along the entire length of the extruded raw pipe, bending of the extruded raw pip due to its own weight can be eliminated, and therefore the axis of the raw pipe can be held with the axis in agreement with the axis of the die from the start of drawing to the end irrespective of the length of the raw pipe. Thereby, the physical relationship of three members of the die, the plug, and the extruded raw pipe during the drawing process can be stabilized from beginning to end, which enables assured manufacturing of an aluminum pipe (drawn pipe) with little deviation.

In the invention as recited in the aforementioned Item [13]since a groove parallel to the axis is formed on the external peripheral surface of the core, the rearward discharging of the lubricating oil can be facilitated during the drawing, which enables smooth drawing especially.

In the invention as recited in the aforementioned Item [14], an aluminum pipe (drawn pipe) excellent in surface smoothness with no variation in roundness, thickness, etc., can be manufactured assuredly.

In the invention as recited in the aforementioned Item [15], an aluminum pipe having further improved surface smoothness can be manufactured.

In the invention as recited in the aforementioned Item [16], since straightening of the aluminum pipe is performed using a roll straightening machine after cutting off a chucked portion of the aluminum pipe which can be a foreign substance generation source, foreign substances will not be brought into the roll straightening machine, thereby enabling the straightening of the aluminum pipe without causing any blemishes due to the foreign substances. Furthermore, since the excising of the chucked portion is performed by a press cutting method, no cut particle will be generated at the time of the excising. Therefore, the straightening of the aluminum pipe can be performed without causing any blemish due to the cut particles.

In the invention as recited in the aforementioned Item [17], since the aluminum pipe is washed using a solvent with a KB value of 20 or more within three days after the drawing, almost no oily lubricant remains on the surface of the aluminum pipe, which in turn dramatically reduces repelling of photosensitizing agent. Thus, a photosensitive layer can be formed uniformly to thereby further improve image quality.

In the invention as recited in the aforementioned Item [18] rising of convex defects on the aluminum pipe surface can be controlled. As a result, leaks of a photosensitive drum due to raised convex defects and generation of defects at the time of forming a photosensitive layer can be prevented effectively.

In the invention as recited in the aforementioned Item [19], occurrence of surface roughness of an aluminum pipe can be prevented certainly while securing sufficient detergency.

In the invention as recited in the aforementioned Item [20], an aluminum pipe suitable for a photosensitive drum for use in electrophotographic devices such as copying machines, printers and facsimile machines can be manufactured.

In the invention as recited in the aforementioned Item [21], an aluminum pipe excellent in surface quality can be provided.

In the invention as recited in the aforementioned Item [22], a photosensitive drum substrate excellent in surface quality suitable for photosensitive drums for use in electrophotographic devices such as copying machines, printers and facsimile machines can be provided.

In the invention (the manufacturing apparatus) as recited in the aforementioned Item [23], an aluminum pipe with no surface defect such as white peeling can be manufactured, which in turn can manufacture an aluminum pipe excellent in surface quality at good manufacturing efficiency.

In the invention as recited in the aforementioned Item [24], it is possible to convey an extruded raw pipe while maintaining the good surface state without causing any damage on the surface.

In the invention as recited in the aforementioned Item [25], since a main fiber constituting the felt is an aramid fiber, the burning and adhering of the fiber of the felt layer to the extruded raw pipe surface (high temperature state) can be more assuredly prevented.

In the invention as recited in the aforementioned Item [26], an aluminum extruded raw pipe with a correctly specified desired length can be manufactured.

In the invention as recited in the aforementioned Item [27], occurrence of surface defects such as white peelings can be assuredly prevented.

In the invention as recited in the aforementioned Item [28], an aluminum pipe excellent in surface quality can be provided.

In the invention as recited in the aforementioned Item [29], a photosensitive drum substrate excellent in surface quality suitable for use in photosensitive drums for use in electrophotographic devices such as copying machines, printers and facsimile machines can be provided.

In the invention as recited in the aforementioned Item [30], a photosensitive drum capable of forming an excellent image suitable for use in electrophotographic devices such as copying machines, printers, and facsimile machines can be provided.

In the invention as recited in the aforementioned Item [31], an electrophotographic device capable of realizing excellent image quality can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a partially enlarged view showing a die bearing portion of an extruding die, FIG. 1B is an enlarged cross-sectional view taken along the line Ib-Ib in FIG. 1A, and FIG. 1C is an enlarged cross-sectional view taken along the line Ic-Ic in FIG. 1A.

FIG. 2 is a cross sectional view showing an example of a porthole die for extruding an extruded raw pipe.

FIG. 3 is a schematic plan view showing a manufacturing apparatus of this invention.

FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3.

FIG. 5 is a cross-sectional view showing a supporting roller.

FIG. 6 is a cross-sectional view showing an example of a drawing processing device.

FIG. 7A, FIG. 7B and FIG. 7C are a perspective view showing a core, respectively.

FIG. 8 is a cross-sectional view showing another example of a drawing processing device.

FIG. 9 is an explanatory view for explaining a definition of an external diameter reduction rate and a cross-sectional area reduction rate.

FIG. 10A is an enlarged vertical cross-sectional view showing a principal portion of a drawing plug, and FIG. 10B is an enlarged vertical cross-sectional view showing a principal portion of a drawing die.

FIG. 11 is a vertical cross-sectional view showing a drawing process metal mold in which the drawing plug and the drawing die shown in FIG. 10 are combined.

FIG. 12A is partial cross-sectional side view showing a chucked portion cut off step, and FIG. 12B is a side view showing a correction step.

FIG. 13A is a cross-sectional view showing an example of an ultrasonic washing machine. FIG. 13B is a cross-sectional view showing another example, and FIG. 13C is a partially broken perspective view showing still another example.

FIG. 14 is an optical microscope photograph showing a surface of an aluminum drawn pipe manufactured with a conventional method, wherein FIG. 14A is a 37.5 times enlarged photograph, and FIG. 14B is a 100 times enlarged photograph.

BEST MODE FOR CARRYING OUT THE INVENTION

A manufacturing method of an aluminum pipe excellent in surface quality according to this invention will be explained in the order corresponding to the steps.

Initially, a billet made of aluminum is extruded to obtain an aluminum extruded raw pipe 4 (extrusion step).

In executing this extrusion, it is preferable to perform the extrusion using an extruding die having the following structure. That is, it is preferable to perform the extrusion using an extruding die in which a length L of a die bearing portion in an extruding direction forming an external surface of the aluminum extruded raw pipe is 5 mm or shorter and a relationship between a center line average roughness Ra(Y) of the bearing portion in a peripheral direction thereof and a center line average roughness Ra(X) of the bearing portion in the extrusion direction is set to Ra(Y)<Ra(X).

At this time, the type of extrusion is not especially limited, and can be an extrusion using a porthole die or a mandrel extrusion. An example of a porthole die used for a porthole extrusion is shown in FIG. 2. In this FIG. 2, “1” denotes a female die and “2” denotes a male die. The female die 1 has at its central portion a penetrated extrusion hole 11, and the inlet side peripheral surface of the extrusion hole is defined as a circular bearing portion 12. The reference numeral “13” denotes a relief portion. On the other hand, a male die 2 has at its central portion a forming protrusion 21 round in cross-section, and a circular bearing portion 22 is formed on the tip end peripheral surface of the forming protrusion 21. The reference numeral “23” denotes a passage pore for passing an aluminum billet. The female die 1 and the male die 2 is combined with the tip end of the forming protrusion 21 of the male die 2 disposed in the extrusion hole 11 of the male die 1, whereby the bearing portions 12 and 22 of both the dies face with each other via an annular forming gap 3.

In this die, the length of the bearing portion for forming an external peripheral surface of an aluminum extruded raw pipe, i.e., in the die shown in FIG. 2, the length L of the female bearing portion 12 in the extruding direction (shown by an arrow X in FIG. 1) is 5 mm or shorter and a relationship between a centerline average roughness Ra(Y) of the bearing portion in a peripheral direction (shown by an arrow Y in FIG. 1) and a centerline average roughness Ra(X) of the extruding direction is set to Ra(Y)<Ra(X). If the length of the bearing portion 12 in the extruding direction exceeds 5 mm, the resistance at the time of the extruding becomes large, and therefore the forming cannot be performed without increasing the extrusion force. The more preferable range of the length of the bearing portion 12 in the extruding direction is 3 mm or shorter. On the other hand, if the length of the bearing portion 12 in the extruding direction is too short, defects such as breakage of the bearing portion due to the deteriorated strength or unstableness of the bearing portion due to the deformed shape may occur easily. Therefore, it is preferable to secure the length of 1 mm or more.

Since the relationship is set to Ra(Y)<Ra(X), the aluminum particles adhered/deposited on the bearing portion are easily caught in the grooves on the surface of the bearing portion, and therefore adhesion/shift of the aluminum particles to the surface of the extruded raw pipe can be controlled. The method for setting it to Ra(Y)<Ra(X) is not specifically limited, but a method of grinding along the peripheral direction (Y direction) as shown in FIG. 1 using a diamond file can be exemplified.

Furthermore, as the extruding die, it is preferable to use an extruding die which fulfills the following conditions, That is, it is preferable that an extruding die has a bearing portion 12 formed of superhard material and the surface roughness of the bearing portion 12 is adjusted to 5 to 30 μm in Ry (maximum height). Specifying the surface roughness so as to fall within the aforementioned specific range facilitates a formation of a thin film of extruding material on the surface of the bearing portion 12. This causes the bearing portion 12 to be uniformly covered with the film of the same composition as the extruding material. As a result, the affinity of the bearing portion 12 and the extruding material improves, easing the burning at the time of extrusion, which improves the surface smoothness of the extruded raw pipe. If Ry is less than 5 μm, a film forming effect becomes poor, and therefore it is not preferable. On the other hand, if Ry exceeds 30 μm, the surface smoothness deteriorates, and therefore it is not preferable. It is especially preferable that the surface roughness of the bearing portion 12 is adjusted such that Ry (maximum height) is 10 to 20 μm. Such prescribed surface roughness of the bearing portion can be easily obtained, for example, by controlling the particle diameter of the ball used in a shot-blasting method and the shot time. As to the superhard material forming the bearing portion 12, it is not specifically limited so long as it can be used as normal die material, such as various cemented carbide and ceramics. The above-mentioned Ry (maximum height) is specified by JIS B0601.

Next, the aforementioned extruded aluminum extruded raw pipe is cut at a position within 10 m from the discharge position of the extruding die to obtain an aluminum extruded raw pipe 4 with a length of 10 m or shorter (cutting step). That is, the cutting is performed by setting the distance Q from the discharge position M of the extruding die of the extruding machine 24 to the cutting position N with the cutting machine 25 to 10 m or shorter and executing the cutting so that the length R of the aluminum extruded raw pipe 4 obtained by cutting with the cutting machine 25 is 10 m or shorter (See FIG. 3).

The schematic plan of the equipment in connection with the extruding step and the cutting step is shown in FIG. 3. In FIG. 3, the reference numeral “24” denotes an extruding machine, “25” denotes a cutting machine, “26” denotes a supporting roller, “27” denotes a control device, and “28” denotes s a speed sensor.

After introducing an aluminum billet from the left, the extruding machine 24 extrudes an aluminum extruded raw pipe 4 from the right end discharge mouth of the extruding die. The cutting machine 25 is disposed at the extruding direction front position of the extruding machine 24 and executes the cutting of the raw pipe 4 while moving in synchronized with the traveling speed of the aluminum extruded raw pipe 4 which is being extruded from the extruding machine 24. The cutting of the aluminum extruded raw pipe with the cutting machine 25 is executed at the position within 10 m from the discharge position M of the extruding die of the extruding machine 24. Between the extruding machine 24 and the cutting machine 25, plural pairs of supporting rollers 26 and 26 are arranged. The pair of supporting rollers 26 and 26 are arranged with the axes crossing perpendicularly in the upwardly opened V shaped manner as shown in FIG. 4, The aluminum extruded raw pipe 4 is supported at the bottom position of the V-shaped portion and conveyed towards the extruding direction front with this supported state. The aforementioned supporting roller 26 is constituted such that a felt made of a synthetic fiber 26 b is circumferentially attached to the external peripheral surface of the tubular roller core portion 26 a as shown in the cross-sectional view of FIG. 5, so that the felt 26 b constituting the external peripheral surface comes into contact with the extruded raw pipe 4 to support the pipe. In this embodiment, an aramid fiber is used as a main fiber constituting the felt 26 b.

Speed sensors 28 and 28 are arranged at the side portions of the aluminum extruded raw pipe 4 which is being extruded from the extruding machine 24. Based on the information on the traveling speed of the aluminum extruded raw pipe 4 obtained from these speed sensors 28 and 28, the control device 27 controls the execution of the cutting operation of the cutting machine 25. That is, the extruded raw pipe 4 is cut at the timing such that the length R of the aluminum extruded raw pipe 4 obtained by the cutting with the cutting machine 25 becomes 10 m or shorter.

As mentioned above, by cutting the extruded aluminum extruded raw pipe 4 at a position within 10 m from the discharge position M of the extruding die to obtain an aluminum extruded raw pipe 4 with a length R of 10 m or shorter, and then subjecting the pipe to the subsequent drawing processing, an aluminum drawn pipe 5 with no surface defect such as white peeling can be manufactured, which in turn can manufacture an aluminum pipe 5 excellent in surface quality at high manufacturing efficiency. The reason that occurrence of surface defects such as white peelings can be prevented is assumed that the contact time of the high temperature extruded raw pipe immediately after extrusion to the surface of the supporting roller is shortened to thereby effectively prevent the fiber of the felt layer from burning and adhering to the raw pipe surface. Among other things, it is preferable that the extruded aluminum extruded raw pipe 4 is cut at a position within 10 m from the discharge position M of the extruding die to obtain an aluminum extruded raw pipe 4 with a length of 1 to 6 m. More preferably, the extruded aluminum extruded raw pipe 4 is cut at a position within 7 m from the discharge position M of the extruding die to obtain an aluminum extruded raw pipe 4 with a length of 2 to 5 m.

As the aluminum billet to be introduced in the extruding machine 24, although it is not specifically limited, it is preferable to use an aluminum billet consisting of Mn: 1.1 to 1.6 mass %, Si; 0.7 mass % or less, Fe: 0.8 mass % or less, Cu: 0.04 to 0.21 mass %. Zn: 0.11 mass % or less, and the balance being aluminum and inevitable impurities. In this case, there is an advantage that an aluminum pipe especially suitable for photosensitive drums can be manufactured.

It is preferable that the peripheral directional surface roughness of the aluminum extruded raw pipe 4 obtained by the cutting falls within the range of from 0.5 to 10 μm in Ry (maximum height). If the surface roughness exceeds 10 μm in Ry (maximum height), thin wrinkle defects tend to be generated on the surface of the aluminum pipe obtained by executing a drawing process. The may cause coating stagnation at the time of applying a thin film of a photosensitive layer to produce a photosensitive drum. On the other hand, if the surface roughness is less than 0.5 μm in Ry, the extruded raw pipe is excessively smooth, causing an introduction of the lubricating oil in between the drawing die and the raw pipe at the time of the drawing process, which in turn tends to form hole-like defects due to oil pits on the surface of the aluminum pipe. The especially preferable lower limit of the surface roughness of the extruded raw pipe 4 in the peripheral direction thereof is 1 μm in Ry, and the upper limit thereof is 7 μm in Ry.

The means for specifying the surface roughness of the aluminum extruded raw pipe 4 in the peripheral direction thereof so as to fall within the range of from 0.5 to 10 μm in Ry is not limited. For example, a mean for specifying the length of the bearing portion of the extruding die in the extruding direction thereof or for controlling the extrusion speed below a predetermined value can be exemplified.

Next, the aluminum extruded raw pipe 4 obtained by the cutting is subjected to a drawing process to thereby obtain an aluminum pipe (aluminum drawn pipe) 5 (drawing step).

In this drawing step, the out aluminum extruded raw pipe 4 is introduced between the drawing die 31 and the drawing plug 33 and drawn while supplying lubricating oil of 200 cst or less between the drawing die 31 and the extruded raw pipe 4. It is preferable to execute the drawing processing such that the external diameter reduction rate from an extruded raw pipe 4 to an aluminum pipe 5 becomes 30% or less and the cross-sectional area reduction rate becomes 5% or more.

If lubricating oil of high viscosity is used, the lubricating oil introduced in between the drawing die 31 and the extruded raw pipe 4 tends to form oil pits, causing concave defects. Using lubricating oil of 200 cst or less in viscosity suppresses the formation of the oil pit, which sufficiently prevents the generation of concave defects on the aluminum pipe (drawn pipe) 5. It is especially preferable that the viscosity of the lubricating oil is 100 cst or less. As lubricating oil of 200 cst or less in viscosity, mineral-oil series lubricating oil and oil-and-fats series lubricating oil can be exemplified.

The external diameter reduction rate and the cross-sectional area reduction rate are defined by the following formula, respectively (see FIG. 9).

External diameter reduction rate (%)=(Do−D)/Do×100

Cross-sectional area reduction rate (%)=(So−S)/So×100

If the external diameter reduction rate exceeds 30%, the die blemish of the extruded raw pipe 4 is crushed to cause a protruded angular portion, which in turn easily causes generation of burr-shaped or eave-shaped defects on the surface of the drawn pipe 5. Therefore, it is not preferable. If the cross-sectional area reduction rate is less than 5%, the die blemish will not be fully closed at the time of the drawing, which may cause concave defects, and therefore it is not preferable. It is more preferable that the external diameter reduction rate is 10% or less and the cross-sectional area reduction rate is 20% or more.

At the drawing step, in other words, at the time of subjecting an aluminum extruded raw pipe to a drawing process by drawing the cut aluminum extruded raw pipe 4 in between the drawing die 31 and the drawing plug 33, as the rod 32 for supporting the drawing plug 33, it is preferable to use a rod 32 having one or a plurality of cores 6 which come into contact with the internal peripheral surface of the extruded raw pipe 4 arranged along the entire length of the extruded raw pipe 4 (FIGS. 6 to 8).

The core 6 equipped to the rod 32 prevents the bending of the raw pipe 4 by its own weight by coming into contact with the internal peripheral surface of the extruded raw pipe 4. By providing such cores 6 in the range covering the entire length of the raw pipe 4, it becomes possible to keep the axis of the raw pipe 4 in agreement with the axis of the die 31 from the start to the end of the drawing. By supporting the raw pipe 4 as mentioned above, the physical relationship of the three members, i.e., the die 31, the plug 33, and the raw pipe 4, can be remained unchanged during the drawing process. Thus, the deflection of the aluminum drawn pipe 5 can fully be restrained.

The core 6 can be of any shape so long as it prevents the bending of the extruded raw pipe to keep the alignment of the axes of the drawing die 31 and the raw pipe 4. Generally cylindrical shaped cores 6 a, 6 b and 6 c as shown in FIG. 7 can be exemplified. In the case of the cores 6 a, 6 b and 6 c of such a shape, by being penetrated by a rod 32 at the center of the core, the entire circumference of the core 6 a, 6 b and 6 c will come into contact with the internal periphery of the raw pipe 4, resulting in stable holding force. In the case of the core 6 a having a smooth external peripheral surface as shown in FIG. 7A, a large contact area to the raw pipe 4 can be obtained, resulting in large holding force. On the other hand, the drawing lubricating oil cannot be easily released backwards. Therefore, it is preferable that the core has grooves 7 parallel to the axis on the external peripheral surface as shown in FIGS. 7B and 7C. The core 6 b shown in FIG. 7B has grooves 7 formed on the entire external peripheral surface and therefore it is excellent in lubricating oil release efficiency. However, the peripheral directional width of the contact surface 8 which comes into contact with the internal peripheral surface of the raw pipe 4 is narrow and therefore the force for holding the raw pipe 4 is small. On the other hand, the core 6 c shown in FIG. 7C has grooves 7 formed at intervals on the external peripheral surface, and the peripheral directional width of the contact surface 8 which comes into contact with the internal peripheral surface of the raw pipe 4 is wide. Therefore, the force for holding the raw pipe 4 is large and the lubricating oil can be released smoothly. Therefore, in cases where grooves 7 are formed on the core 6, the shape shown in FIG. 7C is preferable. In FIGS. 7A, 7B and 7C, each core 6 a, 6 b and 6 c is illustrated as a short core. However, the cross-sectional shape can be applied to a long core 6 e.

The material of the core 6 is not specifically limited so long as it is elastic material which does not cause any damage on the extruded raw pipe 4. The preferable material is resin such as nylon, polyvinyl chloride, polyethylene, and polypropylene.

The cores 6 are preferably attached to the rod 32 along the entire length of the raw pipe 4 to secure the stable physical relationship of the three members, i.e., the drawing die 31, the drawing plug 33 and the raw pipe 4. The attachment along the entire length can be performed by attaching a plurality of short cores 6 d at certain intervals as shown in FIG. 6. Alternatively, as shown in FIG. 8, a single long core 6 e can be used. In either case, the bending of the extruded raw pipe 4 can be prevented, and the deflection of the aluminum pipe (drawn pipe) 5 can be fully restrained.

Furthermore, at the drawing step, in other words, at the time of subjecting a cut aluminum extruded raw pipe to a drawing process by drawing the cut aluminum extruded raw pipe 4 in between the drawing die 31 and the drawing plug 33, as the drawing die 31, it is preferable to use a drawing die in which the approach angle is set so as to fall within the range of from 10 to 40° and the bearing length is set so as to fall within the range of from 8 to 25 mm. On the other hand, as the drawing plug 33, it is preferable to use a drawing plug in which the approach angle is set so as to fall within the range of from 6 to 10° and the bearing length is set so as to fall within the range of from 1.5 to 3 mm (see FIGS. 10 and 11).

FIGS. 10 and 11 show a drawing die 31 and a drawing plug 33 for a ball drawing type. The drawing die 31 is comprised of a die case 41 and a die main body 42 integrally fitted in the die case 41 and is made of die steel, hard metal, ceramics or the like, and has a die hole 43 in the center, an approach portion 44. It also has a bearing portion 45 and a relief portion 46 continuing from the periphery of the die hole 43. It is preferable that the approach angle (θ₁) of the approach portion 44 is set so as to fall within the range of from 10 to 40°. If the approach angle is less than 10°, the drawing processing degree is small, and therefore it is hard to attain a circularity of the aluminum pipe 5. On the other hand, if the approach angle exceeds 40°, it becomes difficult to realize surface smoothness of the aluminum pipe 5, and therefore it is not preferable. Furthermore, the length 11 of the bearing portion 45 defining the external diameter of the aluminum pipe 5 is preferably set so as to fall within the range of from 8 to 25 mm. If the length of this bearing portion 45 is less than 8 mm, the circularity and wall thickness of the aluminum pipe 5 becomes uneven, resulting in unstable dimension. Therefore, it is not preferable. On the other hand, if the length of the bearing portion 45 exceeds 25 mm, burning occurs, which may result in deteriorated surface smoothness of the aluminum pipe 5. Therefore, it is not preferable.

The drawing plug 33 also has an approach portion 51, and a bearing portion 52 and a relief portion 53 continuing from the approach portion 51. It is preferable that the approach angle (θ₂) of the approach portion 51 of the plug 33 is set so as to fall within the range of 6 to 10°. If the approach angle is less than 6°, it becomes hard to attain the circularity of the aluminum pipe 5. Therefore, it is not preferable. On the other hand, if the approach angle exceeds 10°, the circularity and wall thickness of the aluminum pipe 5 becomes uneven, resulting in unstable dimension. Therefore, It is not preferable. Furthermore, it is preferable that the length (12) of the bearing portion 52 of the plug 33 is set so as to fall within the range of from 1.5 to 3 mm. If the length of the bearing portion 52 is less than 1.5 mm, it becomes hard to attain the circularity of the aluminum pipe 5. Therefore, it is not preferable. On the other hand, if the length of the bearing portion 52 exceeds 3 mm, burring occurs, which may result in deteriorated surface smoothness of the aluminum pipe 5. Therefore, it is not preferable. It is needless to say, but the external diameter dimension of the bearing portion 52 of the plug 33 and the internal diameter dimension of the bearing portion 45 of the die 31 are defined by the external and internal diameters and the wall thickness of the aluminum pipe 5 to be manufactured.

At the time of the drawing process, the aforementioned drawing die 31 and drawing plug 33 are combined such that the peripheral surface of the bearing portion 52 of the plug 33 faces the peripheral surface of the generally longitudinal central portion of the bearing 45 of the die 31 via a gap portion corresponding to the prescribed wall thickness of the aluminum pipe 5 as shown in FIG. 11, to thereby constitute a drawing processing die 54. The extruded raw pipe 4 extruded by the extruding machine is drawn with the die to reduce the diameter as shown by a chain line shown in FIG. 11. Although the drawing can be performed only one time to obtain an aluminum pipe 5, it is preferable to execute drawing repeatedly plural times to gradually reduce the diameter to thereby obtain an aluminum pipe 5. Especially, it is preferable to execute drawing twice to obtain an aluminum pipe 5.

In the above explanation, although the drawing is performed by a ball drawing method it is not limited to the above. The drawing can be performed by a floating plug drawing method in which the plug is not fixed.

Furthermore, in the drawing step, it is preferable to carry out the drawing, etc., while fulfilling the following conditions. That is, it is preferable that the drawing is performed by drawing the aluminum extruded raw pipe 4 having a crystal grain whose average length in a drawing direction is 60 μm or more on a surface of the aluminum extruded raw pipe obtained by the cutting so that the average length of the crystal grain in the drawing direction becomes 1.3 times or more, thereby obtaining an aluminum pipe having a crystal grain whose average length in the drawing direction exceeds 300 μm. The reason of using an aluminum extruded raw pipe 4 whose average length of the surface crystal grain in the drawing direction is 60 μm or more is as follows. If it is less than 60 μm, it becomes difficult to attain the average length of the surface crystal grain exceeding 300 μm in the drawing direction by the subsequent drawing processing. The longer the length of the crystal grain of the aluminum extruded raw pipe 4 is, the more the draw ratio at the subsequent drawing processing, i.e., the processing degree to attain the average length of the crystal grain exceeding 300 μm in the drawing direction can be decreased. However, as for the draw ratio of the drawing processing, it is desirable to carry out such that the average length of the surface crystal grain in the drawing direction becomes 1.3 or more times. If the draw ratio is less than 1.3 times, even if the crystal grain of the aluminum extruded raw pipe 4 is large, It becomes difficult to remove minute irregularities such as die lines produced on the surface of the raw pipe 4 by the drawing process, resulting in difficulty in attaining a mirrored surface. Therefore, it is not preferable. The more preferable draw ratio is 1.5 to 2.5 times. In the meantime, the adjustment of the average length of the crystal grain of the surface of the aluminum extruded raw pipe 4 can be performed by adjusting the cold drawing processing degree and the annealing temperature at the time of executing the cold drawing of the extruded raw pipe 4 and then annealing it at above the recrystallization temperature.

Next, the straightening of the aluminum pipe 5 obtained via the above-mentioned drawing step is performed. This straightening is preferably performed as follows. That is, after cutting off the chucked portion 57 of the aluminum pipe obtained by the above-mentioned drawing process by a press cutting method, it is preferable to execute the straightening of the aluminum pipe using a roll correction machine 61. Initially, the chucked portion 57 of the extruded raw pipe 4 is inserted in the die hole 43 from the back side of the drawing die 31, and the chucked portion 57 is chucked with the chucking portion of the carriage 58. Then, drawing is executed by moving the carriage 8 in the front direction (see FIGS. 6 and 8). At the chucked portion 57 after the drawing, dirt adheres in a concentrated manner and burrs due to the bite by the chuck are generated. Therefore, before executing the straightening, the cutting off of the chucked portion 57 is performed. In detail, as shown in FIG. 12A, the end portion of the aluminum drawn pipe 5 located at the side of the chucked portion 57 is inserted into dies 59 and 59, and then the chucked portion 57 is cut off by lowering a cutting blade 60. Since the cutting is performed by the cutting-off blade 60, no particle will be generated. Thereafter, the aluminum drawn pipe 5 is inserted into a roll correction machine 61 from one end of the aluminum drawn pip 5 to be straightened by the function of the internal correction rolls 62 (see FIG. 12B), Since the aluminum drawn pipe 5 is supplied into the roll correction machine 61 after the chucked portion 57 is cut off without generating cut particles, foreign substances such as dirt, aluminum waste and cut particles will not be brought into the roll correction machine 61. Accordingly, no blemish will be generated on the aluminum drawn pipe 5 during the straightening.

Next, the straightened aluminum pipe 5 will be washed. This washing is to remove the aforementioned lubricating oil. This washing is preferably performed as follows. That is, it is preferable that the aluminum pipe 5 is washed with a solvent with KB (kauri-butanol) value of 20 or more within three days after the drawing. The reason of performing the solvent washing within three days after the drawing is as follows. That is, if a certain time has passed after the drawing, the volatilization ingredient contained in the oily lubricant used at the time of the drawing will be volatilized, causing solidification of the lubricant hard to be removed. If three days have passed, it becomes difficult to remove it even if a solvent having high degreasing power is used. It is preferable to execute the washing as soon as possible after the drawing, and the earlier washing enables complete removal with a solvent having less degreasing power.

The KB (kauri-butanol) value of the solvent represents solvent dissolution ability, i.e. degreasing power, and is expressed by the amount mL of an examination solvent dropped to a solution of 20 g that natural kauri gum of long is dissolved by butanol of 500 g at 25 degrees C. until the solvent becomes clouded or causes deposit. Higher KB value means larger dissolution ability. At this washing step, it is preferable to execute the washing using a solvent with the KB value of 20 or more. This is because a solvent having small dissolution ability with the KB value of 20 or less cannot fully remove oily lubricating oil even if the washing is performed within three days after the drawing. As a solvent with the KB value of 20 or more, kerosene (30), cyclohexane (60) toluene (100), aromatic series naphtha (50-80), and non-aromatic series naphtha (20-30) can be exemplified. Especially, it is preferable to use a solvent with the KB value of 25 or above. Although the concrete washing technique is not specifically limited, an immersing method, and a shower method can be exemplified.

Next, finishing washing is further performed. As this finishing washing, it is preferable to perform the following ultrasonic washing. That is, it is preferable to execute the ultrasonic washing of the aluminum tube by setting the relationship between the frequency f (kHz) of the ultrasonic wave of the ultrasonic oscillator and the ultrasonic washing time T (minute) to f×T≦120 (kHz·min). By executing the washing under the conditions, the rising of the convex-like defects of the surface of the aluminum pipe 5 can be prevented. The reasons are assumed as follows. That is, it is assumed that the product fT of the frequency f of the ultrasonic wave (kHz) and the ultrasonic washing time T (minute) seems to be related to the washing energy. If f×T>120, it is assumed that the energy is too large and therefore convex-like defects will be hit in the raising direction. Among other things, it is especially preferable to set the relation to f×T≦100 (kHz·min). On the other hand, if fT is too small, the washing effect becomes poor. Therefore, it is preferable to set the relation to f×T≧2 (kHz·min),

Furthermore, it is more preferable to execute the aforementioned ultrasonic washing by setting the relation between the output of the ultrasonic oscillator P(W) and the ultrasonic oscillation area S (cm²). i.e., the area of the vibrator to 0.1≦P/S≦1.0 (W/cm²). If 0.1>P/S (W/cm²), there is a possibility that the washing effect deteriorates irrespective of the value of fT, and therefore it is not preferable. On the other hand, if it is P/S>1.0 (W/Cm²), there is a possibility that the surface of an aluminum pipe 5 is damaged, which may cause increased leak. Therefore, it is not preferable.

Although the above-mentioned ultrasonic washing washes the aluminum pipe as a member to be washed by sending an ultrasonic wave into the washing liquid, the irradiation method of the ultrasonic wave in the washing bath is not specifically limited. For example, various kinds of washing machines such as a thrown-in type shown in FIG. 13A, an adhesion type shown in FIG. 13B, or a vibration transmission type shown in FIG. 13C can be used. In FIG. 13, the reference numeral “71” denotes a washing bath, “72” denotes a plurality of aluminum tubes as members to be washed, “73” denotes a vibrator, and “75” denotes a vibration transmitter. As the washing liquid 75, although a paraffin oil, light oil, alkali, surface-active agent or trichloroethylene is generally used, it is not limited to the above, and a water system, a hydrocarbon system, a chlorine system organic solvent or the like can be used arbitrarily.

Although the distance between the vibrator or vibration transmitter is not specifically limited, the distance is preferably set to 2 to 50 cm.

The aluminum pipe 5 obtained through the aforementioned extruding step, cutting step, drawing step, straightening step, washing step, and finish washing step does not have, on its surface, fine streaky surface defects (white peelings) extending generally in the drawing direction, and is excellent in surface quality. Therefore, it is suitably used for photosensitive drum substrates for use in electrophotographic devices such as copying machines, printers, or facsimile machines.

Next, concrete examples of this invention will be explained.

EXAMPLE 1

A billet consisting of Mn: 1.12 mass %, Si: 0.11 mass %, Fe: 0.39 mass %, Cu; 0.16 mass %, Zn: 0.01 mass %, Mg: 0.02 mass % and the balance being aluminum and inevitable impurities is extruded under the following extrusion conditions to thereby obtain an aluminum extruded raw pipe (external diameter: 32 mm, wall thickness: 1.5 mm). The surface roughness of this aluminum extruded raw pipe in the peripheral direction was 2.5 μm in Ry. The average length of the crystal grain of the surface of the aluminum extruded raw pipe in the drawing direction was 200 μm.

(Extrusion Conditions)

Extrusion temperature: 520° C.,

Extrusion speed: 0.5 m/min,

Extruding die; the port hole die shown in FIGS. 1 and 2 was used. The length L of the die bearing portion in the extruding direction was 3 mm. Moreover, the relationship between the centerline average roughness Ra(Y) of the bearing portion in the peripheral direction and the centerline average roughness Ra(X) of the extruding direction was set to Ra(Y)<Ra(X). The bearing portion was formed of super-hard material, and the surface roughness of the bearing portion was 5.5 μm in Ry.

Next, using the cutting machine 25 shown in FIG. 3, the aluminum extruded raw pipe extruded from the extruding machine 24 was cut at a position of 7 m from the discharge position M of the extruding die to obtain an aluminum extruded raw pipe 4 with a length of 4 m. That is, in FIG. 3, it was set such that Q=7 m and R=4 m. The composition of the fiber constituting the felt 26 b on the surface of the supporting roller 26 was flame-proof fiber; 35 mass % and p-aramid fiber: 65 mass %.

Subsequently, the cut aluminum extruded raw pipe 4 with a length 2.2 m was subjected to a drawing process under the following conditions to obtain an aluminum pipe 5 with an external diameter of 24 mm and a wall thickness of 0.8 mm.

(Drawing Conditions)

Drawing equipment: an equipment shown in FIG. 6 (the shape of the core is shown in FIG. 7B)

Drawing die; as shown in FIGS. 10 and 11

Drawing die: approach angle of 15°, bearing length of 15 mm

Drawing plug: approach angle of 7°, bearing length of 2 nm

Drawing speed: 15 m/min

Number of drawing: 2 times

External diameter reduction rate per one drawing; 16%

Cross-sectional area reduction rate per one drawing; 32%

Viscosity of lubricating oil: 140 cst

Other drawing conditions: Drawing processing was carried out so that the average length of the crystal grain in the drawing direction increases by 1.8 times, and an aluminum pipe having the average length of the surface crystal grain in the drawing direction of 360 μm was obtained.

Next, after cutting off the chucked portion 57 of the aluminum pipe 5 obtained by the aforementioned drawing processing with a press cutting method, straightening of the aluminum pipe 5 using a roll correction machine 61 was performed (see FIG. 12).

Furthermore, after washing the straightened aluminum pipe with toluene (KS value: 100) within one day, the aluminum pipe for photosensitive drums 5 was obtained by carrying out ultrasonic washing under the following conditions.

(Ultrasonic Washing Conditions)

Frequency f of an ultrasonic wave: 37 kHz

Ultrasonic washing time T: 1 minute

f=T=37 kHz·min

Output P of an ultrasonic oscillator; 2,400 W

Ultrasonic oscillation area S: 4.760 cm²

P/S=0.5 W/cm²

EXAMPLES 2 TO 7

An aluminum pipe for photosensitive drums was obtained in the same manner as in Example 1 except that the distance Q from the discharge position M of the extruding die of the extruding machine 24 to the cutting position N by the cutting machine 25 and the length R of the extruded raw pipe 4 obtained by cutting were set to the values as shown in Table 1.

COMPARATIVE EXAMPLE 1

An aluminum pipe of photosensitive drums was obtained by a conventional method. That is an aluminum pipe of photosensitive drums was obtained by setting Q=50 m and R=50 m. TABLE 1 Distance Q from Evaluation the discharge Percent Production position M of the Length R of defective due yielding extruding die to extruded raw to generation rate the cutting pipe after of white as overall position cutting peeling evaluation (m) (m) (%) (%) Example 1 7 4 8 87 Example 2 6 5 6 90 Example 3 5 3 4 92 Example 4 4 2 3 93 Example 5 3 1 2 94 Example 6 9 9 8 87 Example 7 8 5 7 89 Comp. Ex. 1 50 50 30 60

In each Example and Comparative Example, 1,000 pieces of aluminum pipes for photosensitive drums were manufactured, respectively. In each Example, the surface of each of 1.000 pieces of aluminum pipes was observed using an optical microscope to investigate whether white peeling (fine streak surface defects) on the surface was existed, and the number of the good quality pipes was counted. Based on these results, the defective rate (%) due to white peeling was obtained. Moreover, as to these 1,000 pieces of aluminum pipes, in addition to the existence of the white peeling generating, the existence (existence of blemish, etc.) of other surface defects, the degree of straightness, the uneven thickness and the circularity were evaluated to check whether each fulfilled the respective prescribed standards. The rate of passing all of these five evaluations, i.e., the yield rate of manufacturing the aluminum pipe for photosensitive drums (%) was also obtained. These results are shown in Table 1.

As will be apparent from Table 1, in the aluminum pipes of Examples 1 to 7 manufactured by the manufacturing method of this invention, the generating frequency of the white peeling (minute streak surface defects) on the surface was remarkably small, and the defective rate due to generation of the white peeling was reduced notably. Furthermore, in the overall evaluation including existence of other surface defects, degree of straightness, uneven thickness and circularity, the rate of the product yield was improved notably. On the other hand, in the aluminum pipe of Comparative Example 1 manufactured by a conventional manufacturing method, the frequency of generation of white peeling (fine streak surface defects) on the surface was high, and therefore the defective fraction due to white peeling generating was high. Moreover, since the frequency of generation of white peeling was high as mentioned above, the rate of the product yield became low in the overall evaluation.

The term and explanation used herein are used to explain the embodiments of the invention, and this invention is not limited to them. This invention permits any design changes within the scope of claims unless they deviate from the sprit of the invention.

INDUSTRIAL APPLICABILITY

The aluminum pipe according to the present invention and the aluminum pipe manufactured by the manufacturing method of the present invention are excellent in surface quality, and therefore can be suitably used as a photosensitive drum of electrophotographic devices, such as a copying machine, a printer, and a facsimile machine. 

1. A method of manufacturing an aluminum pipe excellent in surface quality by extruding an aluminum billet to obtain an aluminum extruded raw pipe and then drawing the aluminum extruded raw pipe, wherein the extruded aluminum extruded raw pipe is cut at a position within 10 m from a discharge position of an extruding die to obtain an aluminum extruded raw pipe with a length of 10 m or shorter, and the cut aluminum extruded raw pipe is subjected to a drawing process.
 2. A method of manufacturing an aluminum pipe excellent in surface quality, comprising; an extruding step for extruding an aluminum billet to obtain an aluminum extruded raw pipe; a cutting step for cutting the extruded aluminum extruded raw pipe at a position within 10 m from a discharge position of an extruding die to obtain an aluminum extruded raw pipe with a length of 10 m or shorter; and a drawing step for drawing the cut aluminum extruded raw pipe to obtain an aluminum pipe.
 3. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the extruded aluminum extruded raw pipe is cut at the position within 10 m from the discharge position of the extruding die to thereby obtain an aluminum extruded raw pipe with a length of 1 to 6 m.
 4. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the extruded aluminum extruded raw pipe is cut at the position within 7 m from the discharge position of the extruding die to thereby obtain an aluminum extruded raw pipe with a length of 2 to 5 m.
 5. The method of manufacturing an aluminum pipe excellent in surface quality as recited in any one of claims 1 to 4, wherein the extruded aluminum extruded raw pipe is conveyed towards an extruding direction while supporting the raw pipe with a supporting roller having a synthetic fiber felt circumferentially attached on an external peripheral surface of a roller core portion.
 6. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 5, wherein a main fiber constituting the felt is an aramid fiber.
 7. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein, as the aluminum billet, a billet consisting of Mn: 1.1 to 1.6 mass %, Si: 0.7 mass % or less, Fe: 0.8 mass % or less, Cu: 0.04 to 0.21 mass %, Zn: 0.11 mass % or less, and the balance being aluminum and inevitable impurities is used.
 8. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the extruding is performed using an extruding die in which an extrusion directional length L of a die bearing portion defining an external surface of the aluminum extruded raw pipe is 5 mm or shorter and a relationship between a peripheral directional center line average roughness Ra(Y) of the bearing portion and an extrusion directional center line average roughness Ra(X) of the bearing portion is set to Ra(Y)<Ra(X).
 9. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the extruding is performed using an extruding die in which a bearing portion is formed of superhard material and surface roughness of the bearing portion is adjusted to 5 to 30 μm in Ry (maximum height).
 10. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein peripheral directional surface roughness of the aluminum extruded raw pipe obtained by the cutting is 0.5 to 10 μm in Ry (maximum height).
 11. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein, in drawing the aluminum extruded raw pipe after the cutting by pulling the extruded raw pipe between a drawing die and a drawing plug, the drawing is performed while supplying lubricating oil of 200 cst or less in viscosity between the drawing die and the extruded raw pipe so that an external diameter reduction rate from the extruded raw pipe to an aluminum pipe is 30% or less and a cross-sectional area reduction rate is 5% or more.
 12. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein, in drawing the aluminum extruded raw pipe after the cutting by pulling the extruded raw pipe between a drawing die and a drawing plug, as a rod for supporting the drawing plug, a rod provided with one or a plurality of cores coming into contact with an internal peripheral surface of the extruded raw pipe along an entire length of the extruded raw pipe is used.
 13. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 12, wherein a groove parallel to an axis is formed on an external peripheral surface of the core.
 14. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein, in drawing the aluminum extruded raw pipe after the cutting by pulling the extruded raw pipe between a drawing die and a drawing plug, as the drawing die, a die in which an approach angle is set so as to fall within a range of 10 to 40° and a bearing length is set so as to fall within a range of 8 to 25 mm is used, and as the drawing plug, a plug in which an approach angle is set so as to fall within a range of 6 to 10° and a bearing length is set so as to fall within a range of 1.5 to 3 mm is used.
 15. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the drawing is performed by drawing the aluminum extruded raw pipe having a crystal grain whose average length in a drawing direction is 60 μm or more on a surface of the aluminum extruded raw pipe obtained by the cutting so that the average length of the crystal grain in the drawing direction becomes 1.3 times or more, thereby obtaining an aluminum pipe having a crystal grain whose average length in the drawing direction exceeds 300 μm.
 16. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein, after cutting off a chucked portion of the aluminum pipe obtained by the drawing by a press cutting method, straightening of the aluminum pipe is performed using a roll straightening machine.
 17. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the aluminum pipe obtained by the drawing is washed using a solvent with a KB (kauri-butanol) value of 20 or more within three days after the drawing.
 18. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the aluminum pipe obtained by the drawing is subjected to ultrasonic cleaning by setting a relationship between a frequency f (kHz) of a ultrasonic wave of an ultrasonic wave oscillator and an ultrasonic cleaning time T (minute) to f×T≦120 (kHz·min).
 19. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 18, wherein the ultrasonic cleaning is performed by setting a relationship between an output P (W) of the ultrasonic wave oscillator and an ultrasonic oscillation area S (cm²) to 0.1≦P/S≦1.0 (W/cm²).
 20. The method of manufacturing an aluminum pipe excellent in surface quality as recited in claim 1 or 2, wherein the aluminum pipe is an aluminum pipe for photosensitive drums.
 21. An aluminum pipe manufactured by the manufacturing method as recited in any one of claims 1 to
 19. 22. A photosensitive drum substrate made of an aluminum pipe manufactured by the manufacturing method as recited in any one of claims 1 to
 19. 23. An apparatus for manufacturing an aluminum pipe, comprising: an extruding machine; and a cutting machine disposed at an extruding direction front position of the extruding machine and configured to execute cutting of the aluminum extruded raw pipe which is being extruded from the extruding machine while moving in synchronization with a traveling speed of the aluminum extruded raw pipe, wherein the cutting of the aluminum extruded raw pipe with the cutting machine is executed at a position within 10 m from a discharge position of the extruding die of the extruding machine.
 24. The apparatus for manufacturing an aluminum pipe as recited in claim 23, wherein a supporting roller with a synthetic fiber felt circumferentially attached on an external peripheral surface of a roller core portion is disposed between the extruding machine and the cutting machine.
 25. The apparatus for manufacturing an aluminum pipe as recited in claim 24, wherein a main fiber constituting the felt is an aramid fiber.
 26. The apparatus for manufacturing an aluminum pipe as recited in any one of claims 23 to 25, further comprising a control apparatus for controlling execution of an cutting operation of the cutting machine based on information of the traveling speed of the aluminum extruded raw pipe obtained from a speed sensor.
 27. The apparatus for manufacturing an aluminum pipe as recited in any one of claims 23 to 25, wherein the cutting of the aluminum extruded raw pipe with the cutting machine is executed at a position within 7 m from a discharge position of the extruding die of the extruding machine.
 28. An aluminum drawn pipe having substantially no fine thready surface defect extending approximately in a drawing direction on a surface of the aluminum drawn pipe.
 29. A photosensitive drum substrate made of an aluminum drawn pipe having substantially no fine thready surface defect extending approximately in a drawing direction on a surface of the aluminum drawn pipe.
 30. A photosensitive drum with a photosensitive layer formed on an external peripheral surface of the photosensitive drum substrate as recited in claim 22 or
 29. 31. An electrophotographic device constituted by the photosensitive drum as recited in claim
 30. 